Magneto-inductive flow measuring devices utilize for volumetric flow measurement the principle of electrodynamic induction and are known from a large number of publications. Charge carriers of the medium moved perpendicularly to a magnetic field induce a measurement voltage in measuring electrodes arranged essentially perpendicularly to the flow direction of the medium and perpendicularly to the direction of the magnetic field. The measurement voltage induced in the measuring electrodes is proportional to the flow velocity of the medium averaged over the cross section of the measuring tube and is, thus, proportional to the volume flow rate. If the density of the medium is known, the mass flow in the pipeline, respectively in the measuring tube, can be determined. The measurement voltage is usually tapped via a pair of measuring electrodes, which is arranged, relative to the coordinate along the measuring tube axis, in the region of maximum magnetic field strength and where, thus, the maximum measurement voltage is to be expected.
Published international patent application, WO 2004/072590 A1 discloses a magneto-inductive flow measuring device having two coil bodies arranged lying oppositely on a measuring tube. Each coil body comprises a coil and a pole shoe as coil core. The pole shoe extends into a first passageway of the coil body along the coil axis. It includes a protrusion, which is so embodied that the measuring tube is contactable by the pole shoe approximately gap-freely. The coil bodies are prestressed toward one another by means of two field guide-back elements. In this way, the respective pole shoes are pressed against the measuring tube.
German Patent, DE 10 2004 014 300 A1 describes a magneto-inductive flow measuring device as shown in FIGS. 1 and 2.
A flow measuring device of the field of the invention is additionally disclosed in German patent, DE 10 2010 001 393 A1. This flow measuring device is shown in FIGS. 3 and 4. This flow measuring device is distinguished especially by its fast, cost effective and uncomplicated manufacturability.